Electrical power transmitted from a source to a point of use through an electrical distribution system within a home or a commercial building for equipment and operations is a beneficial service. Conventional electrical receptacles within such a distribution system include a pair of slots or apertures aligned with contacts, wherein prongs of an electric plug may be inserted in the pair of apertures to directly engage contacts within the receptacle in an effort to facilitate a desired electrical connection. Since a large percentage of these receptacles are used in residential buildings and are located near the floor, a young child or infant, for example, may insert a small object into either one of the apertures which potentially may result in electrical shock. More particularly, a burn or shock may result when a child's wet mouth enables electrical contact, wherein a path exists from the hot contact through the child to ground, establishing a ground fault.
Besides a child's fingers and mouth, children may insert into receptacles a wide variety of objects made of conductive material including but not limited to a metal articles. Most objects may be everyday household and easily accessible items such as, paper clips, pens wire tools, hairpins, safety pins, keys, forks, knives, screws, nails, tweezers and coins. Since some of these objects may be perceived by parents as safe, parents tend not to restrict access to many of these objects.
Both scenarios present circumstances to be avoided, where possible. As such, the issue of human safety and avoiding hazards has always been considered by the owner of the instant application in developing new products. Further, in an effort to eliminate the foregoing, the National Electrical Code (NEC) now requires tamper-proof electrical receptacles in pediatric environments since electrical shocks often occur in these types of environments. Research studies have shown that many of these incidents happen around meal time, when parents are occupied in the kitchen and children are not well supervised. A National Electrical Manufacturer's Association (NEMA) task force has concluded that every residential building should be required to have tamper-resistant electrical receptacles and ground fault circuit interrupters (GFCI) designed within the electrical distribution system throughout the home.
Presently available circuit interrupter devices, such as the device described in commonly owned U.S. Pat. No. 4,595,894, which is incorporated herein in its entirety by reference, use a trip mechanism to mechanically break an electrical connection between one or more input and output conductors. Such devices are resettable after they are tripped after the detection of a ground fault. The ground fault circuit interrupter, however, only disconnects the circuit after electrical contact is made with a conductor. Thus, without a tamper resistant electrical receptacle, a person may still experience an initial temporary shock.
Numerous child-proof devices have been proposed or are commercially available which are directed to preventing a child from touching the apertures in a receptacle assembly or preventing a child from inserting or removing an electrical plug in or from the apertures. No such device, however, has achieved wide acceptance; therefore, the aforementioned condition remains today. This is primarily due to ineffectiveness of each device, expense, and the lack of ease of use. Foremost among these drawbacks is one of expense. That is, there are conventional devices that may be applied to various receptacles with safety features. However, the added expense required to manufacture such receptacles outweighs the safety advantage.
Prior patents featuring safety electric receptacles have generally comprised attachments for the face plate of an electric receptacle featuring rotatable snap-on or sliding covers for the electric socket opening, such as disclosed by U.S. Pat. Nos. 3,639,886 and 3,656,083 in which the face plate attachments are manually moved for insertion and removal of the plug. These attachments, such as plastic receptacle caps, are generally designed to include plastic plates having a pair of wall receptacle aperture engaging blades. These plastic receptacle caps, however, are unreliable and inefficient. Research in 1997 by the Temple University Biokinetics Laboratory in Philadelphia showed that 47% of the 4 year olds in a test group were able to remove one brand of receptacle caps. For another similar embodiment of an receptacle cap, 100% of the children within the age group of 2 to 4 years of age were able to remove the receptacle cap in many cases in less than 10 seconds. Other disadvantages of plastic receptacle caps include but are not limited to the forgetfulness of adults to reinsert the caps. In addition, receptacles are susceptible to being exposed to a child who may pull a lamp cord, leaving the receptacle unprotected. Furthermore, constant pressure from the plastic blades on the receptacle contacts increase contact distortion, increasing the risk of loose contacts and/or creating poor contacts, resulting in plugs falling out of the receptacle. Moreover, many of the plastic receptacle caps may create choking hazards, since they may fail to pass a choke hazard test described in a UL standard.
Other patents, such as U.S. Pat. Nos. 2,552,061 and 2,610,999 feature overlying slotted slidable plates which must be manually moved to mate the overlying plate slots with the electric receptacle slots or openings for insertion and removal of the plug. Sliding shutter plates offer a better level of protection than receptacle caps. However, none of the sliding shutter plates that are on the market are UL listed. This is primarily due to the fact that they add extra layers of material between the plug prongs and the receptacle contacts which reduces the surface of contact between plug prongs and contacts, causing potential heat rise or arcing which may also be hazardous. Another disadvantage of a manually movable face plate is that a small child, by observation, may learn to expose the electric receptacle.
Thus, a need exists for an simple, effective, efficient, low-cost electrical receptacle that is tamper-proof and does not need continuous manual adjustment. This device must prevent electric shock when one inserts a conductive instrumentality other than the plug of an appliance, while still permitting full surface contact between the plug prongs and contacts and frequent insertion and removal of prongs.
The present invention is directed to overcoming, or at least reducing the effects of one or more of the problems set forth above.